WASHINGTON — The Secret Service prostitution scandal grew Monday to include a 12th member of the U.S. military as the Pentagon suspended the security clearances of all the military personnel who have been implicated. The Secret Service has also taken action against 12 of its employees.

Three Defense Department officials said the 12th military person involved was in Colombia in advance of President Barack Obama's arrival for the Summit of the Americas and was assigned to the White House Communications Agency, a military unit that provides secure communications for the president. The defense officials, who spoke on the condition of anonymity because the investigation is ongoing, said he is an enlisted man. One of the officials said he is in the Army.

Another of the officials said the soldier has been relieved of his duties at the White House.

Meanwhile, the White House still faced fire Monday because of the prostitution scandal. It moved anew to keep itself at arm's length in two ways. Led by its top lawyer, the White House internally investigated and then ruled out misconduct by the White House staff members who helped arrange the president's trip ahead of his arrival in Colombia. Obama's chief spokesman, Jay Carney, sought to make clear that the "White House Communications Agency," which has now been implicated by the widening scandal, is a military unit and not a White House one.

"These are military personnel, staffed by the military, they are not members of the White House staff, they are not chosen by the White House senior staff," Carney said.

Iowa Sen. Chuck Grassley, the top Republican on the Senate Judiciary Committee, sent a letter to the White House asking for the specific details of the White House counsel investigation.

Defense Secretary Leon Panetta said the Pentagon has suspended the security clearances of the dozen military members under investigation in the scandal. The Secret Service had previously revoked the top-secret clearances for the officers involved.

Six Secret Service employees, including two supervisors, have been forced out of the agency amid the scandal that erupted the morning of April 12 when a fight over payment between a Colombian prostitute and a Secret Service officer spilled into the hallway of the Hotel Caribe. They were part of Obama's advance security team in Cartagena. One officer was cleared of serious wrongdoing but will face administrative action, the agency said Friday. The remaining five officers have been suspended.

A twelfth officer was implicated late last week, and on Sunday a Secret Service official confirmed that the officer had been staying at the nearby Hilton, the same hotel where Obama later stayed.

The official, who spoke on the condition of anonymity to discuss the ongoing investigation, said that officer was being investigated for "allegations of misconduct" that may have occurred on April 9. The official would not say if that conduct involved a prostitute.

The Secret Service and investigators from U.S. Southern Command, which organized the military contingent for the security team in Colombia, have been investigating the incident, which involved as many as 20 Colombian women.

A lawyer for the two ousted supervisors, Greg Stokes and David Chaney, has said that whatever may or may not have been happened at the Hotel Caribe did not impact the officers' mission or compromise the president's security. No other agent or military personnel has been named.

Lawmakers have asked investigators for more details about exactly what happened and who was involved.

The chairman of the Senate Homeland Security Committee, Sen. Joseph Lieberman, told "Fox News Sunday" that his panel was launching a "broader investigation" and would send the Secret Service a detailed list of questions about the conduct of its employees on and off duty.

The House Homeland Security Committee has already sent Secret Service Director Mark Sullivan a list of 50 specific questions, including a request for "a comprehensive, minute-by-minute timeline."

"What they were thinking is beyond me," added King, who has also said he expects more officers to lose their jobs.

The issue is expected to move to Capitol Hill in earnest on Wednesday when Homeland Security Secretary Janet Napolitano testifies before the Senate Judiciary Committee for a previously scheduled oversight hearing.

The Southern Command said military investigators have returned from Colombia and will now conduct interviews in the United States.